"Why would U.S. Army Major Nidal Hasan, murderer of 13 people at Ft Hood and a Muslim, be advanced in spite of all the worries over his competence?"
Superiors Ignored Their Worries
... While in medical school at the Uniformed Services University of Health Sciences from 1997 to 2003, Hasan received a string of below average and failing grades, was put on academic probation and showed little motivation to learn.
... In telling episodes from the latter stages of Hasan's lengthy medical education (he took 6 years instead of the customary four to graduate), he gave a class presentation questioning whether the U.S.-led war on terror was actually a war on Islam. And students said he suggested that Shariah, or Islamic law, trumped the Constitution and he attempted to justify suicide bombings...
... Yet no one in Hasan's chain of command appears to have challenged his eligibility to hold a secret security clearance even though they could have because the statements raised doubt about his loyalty to the United States.
... Instead, in July 2009, Hasan arrived in central Texas, his secret clearance intact, his reputation as a weak performer well known, and Army authorities believing that posting him at such a large facility would mask his shortcomings.
The answer: It is political correctness run amuck.